Biosensors are characterised by a physical or chemical signal transducer, which response is activated by a specific interaction between a biochemical structure (which directly or indirectly has been bound to the transducer) and one or several analytes.
Biosensors are used to detect the analyte/analytes and in certain cases also for quantification of the analyte/analytes.
The advantages of the biosensor are that a physical or chemical transducer has been made specific so that a general physical or chemical parameter (e.g. temperature, pH, optical density) can be used for the detection of one specific substance in a complex mixture of non-specific substances.
The limitations of the biosensor are the specificity of the biochemical structure bound to the transducer, the range of specificity and stability, and, that the transducer signal has to be made independent of the background changes in the parameter that the transducer is measuring. In Methods of Enzymology, volume 137, several articles are describing different aspects of biosensors.